Background: Mucinous adenocarcinoma of the colorectum is a rare histological subtype characterized by an abundant mucinous component. Mucinous tumors are frequently diagnosed at an advanced stage, which indicates an aggressive subtype. However, few case reports have been published, and little information is available concerning genetic alterations in mucinous adenocarcinoma.
Case summary: A 76-year-old man underwent en bloc endoscopic submucosal dissection (ESD) for the management of a type 0-Is+IIa lesion. Histological examination revealed an intramucosal mucinous adenocarcinoma with signet-ring cell carcinoma and well-to-moderately differentiated tubular adenocarcinoma. Three years after the ESD, local recurrence was detected by an endoscopic examination, revealing a new 0-Is+IIa lesion with a phenotype similar to the previously resected lesion. Re-ESD was chosen for the management of the recurrent tumor, and the histological examination showed positive tumor infiltration at the vertical margin. Additional surgical resection was performed for the curative treatment. Genetic analysis showed pathogenic alterations in RNF43 and TP53 in the adenoma and an additional SMAD4 alteration in the carcinoma.
Conclusion: This mucinous mucosal adenocarcinoma case was suggested to have an aggressive phenotype and a careful and close follow-up are required.
Keywords: Case report; Colitic cancer pathway; Endoscopic submucosal dissectio; Mucinous adenocarcinoma; Rectal cancer; TP53.
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